Water-Resources Investigations Report 91-4011


Prepared by the

in cooperation with the

                                                     Click here to return to USGS Publications
By Dorothea       Within&on         Hanchar

Water-Resources Investigations Report 91-4011

Prepared in cooperation with the

                                  Nashville, Tennessee
                               U.S. DEPARTMENT OF THE INTERIOR
                                    MANUEL LUJAN, JR., Secretary

                                         U.S. GEOLOGICAL SURVEY
                                            Dallas L. Peck, Director


For additional information   write to:                    Copies of this report can be purchased from:

District Chief                                            U.S. Geological Survey
U.S. Geological Survey                                    Books and Open-File Reports Section
810 Broadway, Suite 500                                   Federal Center, Building 810
Nashville, Tennessee37203                                 Box 25425
                                                          Denver, Colorado 80225
 Abstract      1
 Introduction     1
      Purpose and scope 2
      Acknowledgments        2
 Septic-tank systems 2
 Geohydrology of the study area 3
 Well construction      6
 Data collection and analysis 7
 Effects of septic-tank effluent on ground-water quality   9
      Major inorganic constituents     9
      Nutrients     9
      Organic substances 13
      Optical brighteners     13
      Bacteria     14
 Summary and conclusions 14
 References cited      15

Figure 1. Map showing location of observation wells,
              springs, and surface-water sampling sites in
              Williamson County      4
       2. Map showing location of domestic well and spring in
              Davidson County      5
       3. Stratigraphic column of wells Wm:O-13 and Wm:O-15           8

Table 1. Well construction, yield, and water-level data for observation
           and domestic wells in the study area      7

      2. Water-quality analyses      10


Multiply                                 BY                   To obtain

acre                                   0.004047            square kilometer
foot (ft)                              0.3048              meter
gallon per minute (gal/min)            0.06309             liter per second
pound (lb)                             0.4536              kilogram
square mile (mi2)                      2.590               square kilometer
inch (in.)                            25.4                 millimeter
mile (mi)                              1.609               kilometer

T’emperature in degrees Celsius (“C) may be converted to degrees Fahrenheit (“F) as
                                 “F = 1.8 * “C + 32

Sea level: In this report “sea level” refers to the National Geodetic Vertical Datum of 1929
(NGVD of 1929)--a geodetic datum derived from a general adjustment of the first-order
level nets of both the United States and Canada, formerly called Sea Level Datum of 1929.

                          By Dorothea Withington Hanchar

               ABSTRACT                                     sampled during 1988. Water from one of these
                                                            springs contained optical brighteners, which
                                                            indicates that septic-tank efluent is affecting
      An     investigation    of   the potential
                                                            ground-water quality.
 contamination of ground water from septic tank
systems blasted in bedrock in Williamson and
Davidson Counties, Tennessee, was conducted
 during 1988-89. Water samples were collected                        INTRODUCTION
from domestic and observation wells, springs,
 and St.&ace-water sites in a residential                          Subsurface sewage disposal systems are
subdivision in the northern part of Williamson              the largest sources of wastewater to the
 County near Nashville. The subdivision has a               ground, and are the most frequently reported
 high density of septic-tank field lines installed          causes of ground-water contamination (Miller,
 into blasted bedrock Water samples also were               1980, p. 186). The likelihood of ground-water
 collected from a well located in an area of                contamination by these systems is greatest
Davidson County where field lines were installed            where septic systems are closely spaced as in
 in 5 feet of soil. Samples were analyzed for               subdivided tracts in suburban areas and in
 major inorganic constituents, nutrients, total             areas where the bedrock is covered by little or
 organic carbon, optical brighteners, and                   no soil. In the ‘rocky terrain of Middle
 bacteria. Although results of analyses of water            Tennessee, the field lines of as many as
samples from wells indicate no e@ectof septic-              20 percent of the domestic septic systems are
 tank efluent on ground-water quality at these              installed in blasted bedrock with virtually no
sites, water from          two springs located              soil (Brent Ogles, Tennessee Department of
downgradient from the subdivision had slightly              Health and Environment, Division of Ground
 larger concentrations of nitrite plus nitrate (2.2         Water Protection, oral commun., 1987).
 and 2.7 milligrams per liter N), and much larger           Concern about the effects of these domestic
concentrations of fecal colifonn and fecal                  septic systems on ground-water          quality
streptococci bacteria (2,000 to 3,200 and 700 to            prompted the U.S. Geological Survey, in
 900 colonies per 100 milliliters of sample,                cooperation with the Tennessee Department
respectively), than other wells and springs                 of Health and Environment (TDHE)‘,
<                             _-   .              - -
‘Tennessee Department       of Environment    and Conservation (TDEC) as of 1991.

Division of Water Pollution Control, to initiate        area where field lines were installed in blasted
in 1988 an investigation of the occurrence of           bedrock, although, for comparison, one well
septic-tank effluent in ground water and the            was in an area where field lines were installed
effects of any effluent present on                      in soil averaging about 5 feet in thickness.
ground-water quality. The study area, in                Water from the four springs also was sampled
northern Williamson County and southern                 in April 1989 and analyzed for optical
Davidson County, was selected because most              brighteners to determine if the springs and the
of the septic systems in this area have field           subsurface sewage-disposal systems are
lines installed in blasted bedrock.                     hydraulically connected.

            Purpose and Scope                                        Acknowledgments

     This report presents the results of the                The author thanks Mr. Larry Robinson,
study of ground-water quality in areas of               Environmental Specialist for Williamson
septic tanks in northern Williamson County              County; Mr. Brent Ogles, Environmental
and southern Davidson County. The purpose               Manager, TDHE, Division of Ground Water
of the study was to:                                    Protection; Mr. Tom Petty, Environmental
                                                        Specialist for Wilson          County;    and
     1. Determine if a hydraulic connection             Mr. Christopher Andel, Ms. Karen Grubbs,
        existsbetween septic-tank systemsand            and Dr. Andrew Barrass of the Nonpoint
        the ground-water system and, if so,             Source Program, Tennessee Department of
                                                        Health and Environment, Division of Water
    2. Determine     the potential      for             Pollution Control, for their assistance. Also,
       occurrence or existence of ground-               the author thanks the many homeowners who
       water contamination by septic-system             allowed accessto their land.

     The study included the collection of water                    SEPTIC-TANK
samples from springs, observation wells, and
domestic wells in Williamson and Davidson                            SYSTEMS
Counties for analysis of water-quality
characteristics.     Observation wells were                  A typical septic-tank system consists of
installed in an area where field lines for septic       two parts, the tank itself and field lines
systems were installed in blasted bedrock.              installed into an absorption field. If the tank
These wells were completed in both the                  is properly constructed, only wastewater will
shallow and deep water-bearing zones                    flow through the field lines. Field lines
upgradient from ground-water-discharge                  generally are installed in trenches dug into
points. Samples were collected from these               soils having a minimum thickness of 3 feet,
wells and springs in May 1988, November                 where the bottom of the trench is underlain
1988, and May 1989 to coincide with dry                 by at least 2 feet of soil above the water table
(May) and rainy (November) conditions.                  or creviced bedrock. Where rock crops out at
Water samples were analyzed for bacteria,               the surface, common practice in Tennessee
nutrients, major inorganic constituents,                until June 1990 was to install field lines in
specific conductance, pH, temperature, and              trenches blasted in the bedrock and
total organic carbon, and, in May 1988, for             back-filled with gravel. In Middle Tennessee,
concentrations of organic constituents. Most            limestone formations commonly crop out at
of the water samples were from wells in an              land surface with little or no soil cover.

     Ground water in the carbonate rocks of                   GEOHYDROLOGY
Middle Tennessee typically flows through
solution openings that have developed along                     OF THE STUDY
bedding planes, fractures, and joints (Hollyday                     AREA
and Goddard, 1979). Blasting near-surface
bedrock to install field lines can create
fractures in the limestone that hydraulically               The study area includes two sites, one
connect to an existing solution opening. If            with a high density of septic-system field lines
this occurs, the fracture can provide a conduit        installed in blasted bedrock and another with
from the field lines to the ground-water               field lines installed in soils averaging about
reservoir.                                             5 feet in thickness. The first site is in
                                                       northern Williamson County (fig. 1) and
     Domestic septic-tank effluent typically           includes a subdivision where septic systems
contains elevated concentrations of chloride,          have a high rate of failure both to the surface
sulfate, nitrite plus nitrate, ammonia, organic        and to the ground (Larry Robinson,
nitrogen, total nitrogen, total phosphate, fecal       Williamson County, oral commun., 1987).
coliform and fecal streptococci bacteria, and          Most runoff from the site drains to a central
total organic carbon (TOC) (Canter and               , sinkhole, which in turn is drained by a ditch
Knox, 1985). Concentrations of nitrite plus            blasted in bedrock (fig. 1). The site is
nitrate as nitrogen (N) greater than                   underlain by limestone that is capable of
3 mg/L (milligrams per liter) generally                yielding small quantities of water to wells in
indicate influence of human activity (Madison          the area.
and Burnett, 1985). Elevated concentrations
of chloride, ammonia, and sulfate also have               Three springs lie downgradient of the
been interpreted to be the result of                  septic systems,Wm:O-9 and Wm:O-11, which
septic-tank effluent (Waller and others, 1987;        flow year round, and Wm:O-10, which flows
Pitt and others, 1975). Effluent migration has        only after periods of sustained rain (fig. 1).
been monitored, both vertically and laterally,        Springs Wm:O-9 and Wm:O-11, therefore,
using variations in concentrations of these           discharge water from the water-table aquifer.
constituents (Waller and others, 1987). All of        Discharge of all three springs generally is less
these constituents, however, are commonly             than about 2 gallons per minute.
found in ground water (Aley, 1985). As a
result, unless elevated concentrations are                The second sampling site is located in
present, one cannot confidently determine             southern Davidson County (fig. 2) about
whether a system has been affected by sewage          7 miles northwest of the first site. This site is
(Aley, 1985).                                         in an older neighborhood, where septic
                                                      systems have been in use for as long as
     Common components of septic-tank                 75 years. Septic-system field lines at this site
effluent that are not naturally present in            are installed in soil which generally is 3 to
ground water are fluorescent white dyes used          5 feet thick.    The soil is underlain by
as optical brighteners in laundry soap and            limestone which is capable of yielding small
detergents.      The occurrence of optical            quantities of water to wells in the area.
brighteners in ground water downgradient
from septic-tank field lines is an indicator of           A small spring, Dv:F-2 (fig. 2) lies about
the presence of septic-tank effluent. This            700 feet to the southeast of residential areas
indicator is particularly effective in karst areas    using septic systems. The spring flows year
(Mull and others, 1988; Wilson and others,            round and has a discharge of less than
1988).                                                3 gallons per minute.
    86’42’   30”                                                                                     86’40   ’
36O 00 ’

                       TENNESSEE                      0                    0.5                    1 MILE
                                                                             I                    I
                                                      I                I            I
                                                      0              0.5            1 KILOMETER


                                                          Wm:v4        OBSERVATION WELL AND NUMBER

              SINKHOLE--Hachures   indicate               Wm%8         DOMESTIC WELL AND NUMBER
   Q            depression
 -. . .-      INTERMITTENT STREAM                         Wm:OQ;17 DRY HOLE AND NUMBER
        A                                                 Wm:O- 10
              SURFACE-WATER SAMPLING SITE                     0-v      SPRING AND NUMBER
                AND NUMBER

 Figure      l.--   Location      of observation  wells, springs,  and           surface-water     sampling
                                         sites in Williamson   County.

                                                                  86’ 45 ’ 28”
   86’ 46’ 54”

                        0             1,000    2,000   3,000   FEET
                        I      1     I 1’ 1 ’ I
                        0          200     400  600 METERS


                       a             GENERALIZED SUBDIVISION
                  -     ...A         INTERMITTENT STREAM
                      Dv:F- 1
                           a         DOMESTIC WELL AND NUMBER
                  Dv:F-2g            SPRING AND NUMBER

Figure    2.--   Location  of domestic    well                   and     spring
                      in Davidson County.

     The Williamson County site overlies                 WELL CONSTRUCTION
 limestone with little soil coverage. The
 formations underlying the site are, in
 descending order, the Hermitage Formation,
 the Carters Limestone, the Lebanon
Limestone, and the Ridley Limestone, all of                 Six observation wells were drilled at the
Ordovician age. The Hermitage Formation               Williamson County site (fig. 1) using the
caps the hills.        This formation is a            air-rotary method. Depths of these wells
thin-bedded, silty limestone and acts as a            range from 65 to 185 feet below land surface
confining unit. Field lines completed within           (table 1). Six-inch diameter galvanized steel
the Hermitage Formation are more likely to            casing was set at least 20 feet into bedrock.
fail to the surface than to the subsurface            The rest of the well was completed in rock,
because of the high clay content of this              and left as open bore. A seal of bentonite
formation.     Lower lying parts of the               pellets was installed in the well annulus at the
subdivision are underlain by Carters                  base of the casing to a thickness of at least
Limestone, which is a blocky micritic                  1 foot, and the well annulus at the surface was
limestone and is a probable aquifer. Field            sealed to a depth of 1 foot using cement
lines completed within the Carters Limestone          grout. Of the six observation wells drilled,
are more likely to fail to the subsurface than        two were dry (Wm:O-16 and Wm:O-17), three
to the surface because of the potential               had estimated yields of less than 1 gallon per
occurrence of open fractures and solution             minute (Wm:O-12, Wm:O-13, Wm:O-14), and
openings.                                             one (Wm:O-15) had an estimated yield of
                                                      15 gallons per minute.        All yields were
                                                      measured by discharging water through a
     The Lebanon Limestone acts as a                  flume during the development of the well.
confining unit, but the Ridley Limestone, also
a blocky micritic limestone, is an aquifer. The            Two wells at this site were completed in
two domestic wells in the area are completed          the shallow water-bearing zone, and two wells
in the Ridley Limestone.             A major          were completed in the deep water-bearing
water-bearing zone has been identified at the         zone. The shallow water-bearing zone occurs
contact between the Lebanon Limestone and             at or near the contact between the Carters
the Ridley Limestone at a depth between 130           Limestone and the Lebanon Limestone at a
and 145 feet below land surface.                      depth that ranges between 25 and 30 feet
                                                      below land surface. Wells completed in this
                                                      shallow zone are Wm:O-12 and Wm:O-14
    The Davidson County site overlies the             (table 1). The deep water-bearing zone
Bigby-Cannon    Limestone2, which has                 occurs at or near the contact between the
weathered into a relatively thick soil. This          Lebanon Limestone and the Ridley
formation is a soluble, silt-free limestone.          Limestone, which occurs between 125 and
The Bigby-Cannon Limestone overlies the               145 feet below land surface. Well Wm:O-15
Hermitage Formation. The spring (Dv:F-2)              was completed in this deeper zone (table l),
occurs at the contact between these two               and well Wm:O-13 was completed within the
formations.                                           Ridley Limestone (fig. 3).

*Unit follows usage of Tennessee Division of Geology.

        Table I.--Well construction, yield, and water level data for observation and domestic
                                         wells in the study area

              [0, observation well; D, domestic well; C/L = Carters
                 Limestone/Lebanon Limestone; L/R = Lebanon LimestoneRidley
                 Limestone; *, none; **, well was dry at time of measurement;
                 --, not measured; c, less than]

                             Casing                                                         .
                             depth, in                                                Water level,
                    Type    feet below   Water-         Well depth,      Yield,     May 8, 1989, in
           Well      of        land      bearing       in feet below   in gallons   feet below land
         number     well      surface     zone         land surface    per minute        surface
        Wm:O-12       0         21         c/i            70             cl.0           17.40
        Wm:O-13       0         22         L/R           165             cl.0          83.49
        Wm:O-14       0         25         C/L           105             cl.0          58.66
        Wm:O-15       0         21         L/R           140             15            64.60
        Wm:O-16       0         21          *             65             0              **
        Wm:O-17       0         20                       185              0              **
        Wm:O-7        D          --        L/R           285             --              --
        Wm:O-8        D         21         UR            198             --              --
        Dv:F-1        D          --        L/R           a2oo            --              --

      aApproximate depth.

     Well Wm:O-16 terminated in the                       Site 2 is on the drainage ditch blasted into the
Lebanon Limestone, and well Wm:O-17                       bedrock to drain the sinkhole. Site 4 is on the
terminated in the Ridley Limestone. Neither               small creek downstream from spring Wm:O-9.
well intercepted a water-bearing zone, and as             Site 7 is on a stream that drains the study
of May 1989, both were dry.                               area to the south. Site 6 is on a stream that
                                                          drains the hills to the south and is unrelated
                                                          to the surface-water flow from the study area.
                                                          Samples collected during this period were
              DATA                                        analyzed for fecal coliform and fecal
                                                          streptococci bacteria, temperature, specific
           COLLECTION                                     conductance, alkalinity, pH, major inorganic
          AND ANALYSIS                                    constituents, nutrients, methylene blue active
                                                          substances(MBAS), and total organic carbon.
     Water samples were collected at the                  Samples also were scanned using a gas
Williamson County site in May 1988 from the               chromatograph with a flame ionization
three springs (Wm:O-9, Wm:O-10, Wm:O-11),                 detector (GC/FID) to determine if methylene
two domestic wells (Wm:O-7, Wm:O-S), and                  chloride-extractable organic substances were
four surface-water sites (sites 2, 4, 6, and 7).          present.




33ViLinS   CINV-I MO138   13&i   NI ‘Hld3a

     Ground-water samples were collected             A sample also was collected from domestic
using two different methods -- pumping and           well Dv:F-1 at the Davidson County site.
bailing. Domestic wells were pumped and the          Samples were analyzed for the same
samples were collected at faucets. The               constituents as in November 1988 with the
samples were collected after the specific            addition of bacterial analyses. Results of the
conductance had stabilized to ensure a               analysesfor the three samplings are presented
representative sample. The observation wells         in table 2.
were purged of at least three casing volumes
of water, using a submersible pump.                            EFFECTS OF
Observation well Wm:O-15 was sampled by
pumping. The remaining observation wells,                     SEPTIC-TANK
because of their low yields, were sampled                     EFFLUENT ON
using a stainless-steel bailer. The bailer was
rinsed between samples with deionized water.
     Grab-samples were collected at the
springs. Because of low yields, it was not
possible to collect depth integrated samples.            Wells and springs were sampled on three
                                                     occasions to determine if septic-tank effluent
     Samples were collected a second time in         has affected ground-water quality. The sites
November 1988. Based on the results of the           sampled varied from one sampling event to
first sampling period, sampling sites were           the next, depending on the results of previous
limited to observation wells Wm:O-12,                analyses.
Wm:O-13, and Wm:O-14, and springs,
Wm:O-9 and Wm:O-11.            Temperature,                         Major Inorganic
specific conductance, and pH were measured                           Constituents
in the field and water samples were collected
and shipped to the laboratory for analysis of            Samples collected during the study did not
major inorganic constituents, nutrients, and         exhibit concentrations of any water-quality
total organic carbon. Scans for organic              constituents that decisively indicated effects of
substances were not performed on this suite          septic-tank effluent. Concentrations of ions
of samples because such substanceswere not           such as sulfate, calcium, chloride, and sodium,
detected in any of the samples collected in          which are commonly used as indicators of
May 1988.                                            sewage contamination, were typical of
                                                     uncontaminated ground water (table 2).
     In April 1989, all four springs (three in
Williamson County and one in Davidson
County) were sampled and analyzed for
optical brighteners. These analyses were                                Nutrients
performed to determine if any hydraulic
connection exists between the springs and                 The principal nutrients, nitrogen and
septic-tank field lines.                             phosphorus, are potential indicators of
                                                     ground-water, septic-tank contamination by
    A final suite of samples was collected in        effluents (Miller, 1980; p. 190 and table 23).
May 1989. During this sampling effort,               Most of the sampling in the study was focused
observation wells Wm:O-12, Wm:O-13,                  to determine concentrations of the principal
Wm:O-14, and Wm:O-15, and spring Wm:O-9              speciesof nitrogen (organic, ammonia, nitrite,
were sampled at the Williamson County site.          and nitrate) and phosphorus (organic and

        s!       8           8           8
                                         -.   l2RS .   $Q      Qg           ZQ          %E     z
                                     .          . .      . .    . .          . .         . .
                 ”           ”           ”    ‘21‘     ”       w                        w

2 *. w Ei
 .   . .                                                       cos          s\“x        8% .
                                                                                         .     R.
” -    ”                                                       ti’          w.’         w      ”

I        I           I           I                                          t?E
I        I           I           I                             :z
                                                                        .       .   .

                                                                                        00 z
                                                                                        5;s .
                                                                                         .     z.
                                                               Y            Y           w      ”

                                                               “0           90          “0     D









                         .    .

orthophosphate).    The results of the analyses          inadequate purging of drilling fluid from the
indicated      higher     than    background             adjacent aquifer prior to the November 1988
concentrations of these nutrients in several of          sampling.
the samples (table 2). Elevated nitrite plus
nitrate (1.5 mg/L as N), ammonia (1.3 mg/L
as N), and ammonia plus organic nitrogen                             Organic Substances
(1.8 mg/L     as N)      concentrations    were
measured in water from spring Wm:O-9.                         No synthetic organic compounds were
Concentrations      of    these    water-quality         detected in any of the samples collected.
constituents were not noticeably elevated in             Scans for methylene chloride-extractable
samples from the domestic wells, the other               organic substances were conducted on all
springs, and the surface-water sites sampled in          samples collected at the Williamson County
May 1988.                                                site in May 1988. The scans were conducted
                                                         using a ‘gas chromatograph (GC) equipped
     Some of the samples collected in                    with a flame-ionization detector (FID). The
November 1988, however, did indicate a                   FID is a non-specific detector that responds
possible effect of nutrients from septic-tank            to a broad range of organic substances that
effluent upon ground-water quality. Samples              pass through the GC.       A positive result
from springs Wm:O-9 and Wm:O-11, and                     appears as an anomalous,          compound-
from well Wm:O-12 had slightly elevated                  unidentifiable peak. Peaks were not present
concentrations of nitrite plus nitrate (2.7, 2.2,        in any of the scans of samples from the
and 1.4 mg/L, as nitrogen, respectively) that            Williamson County site.
may have been due to field-line effluent.
Analyses of May 1989, however, indicated no                   Analysis for total organic carbon (TOC)
discernable effect from septic-tank effluent.            is a determination of the total concentration
Although in May 1989, spring Wm:O-9 did                  of organic carbon in a water sample. Analysis
have a nitrite plus nitrate concentration of             for TOC does not separate natural from
1.4 mg/L as nitrogen, the data are inconclusive          synthetic organic carbon occurring in ground
as to whether           the slightly    elevated         water. Concentrations of TOC in septic-tank
concentration of nitrite plus nitrate was due to         effluent can be as high as 69 to 200 mg/L
septic-tank effluent.                                    (Waller and others, 1987; Canter and Knox,
                                                          1986). TOC concentrations measured at sites
     The November 1988 analyses of water                 in Williamson and Davidson Counties ranged
from well Wm:O-13 revealed somewhat                      from 0.5 to 5.7 mg/L.            The highest
 elevated concentrations of ammonia plus                 concentration was measured in water from
 organic nitrogen (2.8 mg/L), total phosphorus           spring Wm:O-9 in May 1988; however,
 (1.4 mg/L, as P), and sulfate (150 mg/L, as             because this concentration is within the range
SO,). These were the highest concentrations              of TOC concentrations for some natural
of these constituents measured in any of the             waters, TOC data cannot be used to confirm
samples from any of the sites. Analyses of               the presence of septic-tank effluent.
samples collected from this well in May 1989
indicated much lower concentrations of these
constituents.    Because of the depth of this                        Optical Brighteners
well and its low yield, purging is difficult;
therefore, the sample collected from this well               To demonstrate whether or not a
in November 1988 possibly did not represent              hydraulic connection exists between field lines
ambient conditions.     Variations in analyses           and the springs in the study area, a qualitative
between samples collected in November 1988               dye test for optical brighteners was conducted.
and May 1989 may be due in part to                       Sampling devices consisting of surgical white

cotton swabs attached to wire secured to a                 Water from the four surface-water sites
concrete base were placed in the discharge of          had fecal streptococci counts ranging from 670
the springs. These swabswere later tested for          to 3,900 colonies per 100 milliliters (mL) of
fluorescence under ultraviolet light (a                sample. Fecal coliform counts in the samples
characteristic of optical brighteners) using           from these sites ranged from 22 to
methods described by Mull and others (1988).           880 colonies per 100 mL of sample.

     Four optical-brightener sampling devices              Water from the three springs (Wm:O-9,
were placed in the three springs (Wm:O-9,              WM:O-10, and WM:O-11) had 700 to 1,800
Wm:O-10, and Wm:O-11) at the Williamson                colonies of fecal streptococci, and 14 to
County site, and in the spring at the Davidson         3,200 colonies of fecal coliform per 100 mL of
County site (Dv:F-2) in April 1989. These              sample. The sample from spring Wm:O-10
devices were retrieved after 3 days. Of the            contained 14 colonies of fecal coliform and
four devices, only the one from spring                 1,800 colonies of fecal streptococci per
Wm:O-9 fluoresced under ultraviolet light,             100 mL of sample.
indicating the presence of optical brighteners
in the discharge. Another device was placed                 Samples from springs had much higher
in spring Wm:O-9, and left for 14 days. The            bacterial counts than those from wells. Water
second swab also fluoresced, confirming the            from spring Wm:O-9 contained 3,200 colonies
presence of optical brighteners which are              of fecal coliform per 100 mL of sample in
commonly found in septic-tank effluent.                May 1988 and 2,700 colonies per 100 mL in
Based on the results of this test, a hydraulic         May 1989. Water from spring Wm:O-11
connection between field lines and spring              contained 2,000 colonies per 100 mL of
Wm:O-9 was shown to exist. Hydraulic                   sample in May 1988. Spring Wm:O-11 is
connection between field lines and the other           located in a cow pasture and is used by cows
springs could not be demonstrated.                     as a source of drinking water; consequently,
                                                       its water quality may be influenced not only
                                                       by septic-tank effluent but also by animal
                   Bacteria                            excreta.

     Both fecal coliform and fecal streptococci            None of the samples from the three
bacteria are present in the gastrointestinal           domestic wells contained fecal coliform or
tract of humans and other warm-blooded                 fecal streptococci bacteria.         Bacterial
animals. The presence of these bacteria in             concentrations in water from the four
natural water indicates degradation by human           observation wells ranged from less than 1 to
or animal waste and may be related to septic-          65 colonies of fecal coliform per 100 mL and
tank waste.                                            from less than 1 to 380 colonies of fecal
                                                       streptococci per 100 mL. The sample from
    Samples collected in May 1988 from                 observation well Wm:O-15 did not contain
domestic wells Wm:O-7 and Wm:O-8, four                 either fecal coliform or fecal streptococcus
surface-water sites, and three springs were            bacteria.
analyzed for fecal streptococci and fecal
coliform. Samples collected in May 1989from
the four observation wells, spring Wm:O-9,                      SUMMARY AND
and domestic well Dv:F-1 also were analyzed
for these bacteria. Sample collection and                       CONCLUSIONS
analyseswere in accordance with the methods
of Britton and Greeson (1987). Results are                 The results of analysesfor major chemical
included in table 2.                                   constituents and nutrients in water from

domestic wells, observation wells, and springs                           REFERENCES
do not conclusively show the presence or
absence of septic-tank effluent in ground                                   CITED
water in northern Williamson County and
                                                        AIey, T.J., 1985, Optical brightener sampling; a reconnaissancetool
southern Davidson County. Concentrations of                      for detecting sewagein karst groundwater: American Institute
constituents commonly thought to be a                            of Hydrology, v. 1, no. 1, p. 45-48.
product of effluent from field lines did not            B&ton, L.J., and Greeson, P.E., eds., 1987, Methods for collection
greatly exceed concentrations common in                          and analysisof aquatic biological and microbiological samples:
natural ground water in the area. Slightly                       U.S. Geological Survey Techniques of Water-Resources
                                                                 Investigations, Book 5, Chapter A4, p. 5367.
elevated concentrations of nitrite plus nitrate         Canter, L.W., and Knox, R.C., 1985, Septic tank system effects on
and total ammonia in spring Wm:O-9 could                        ground water quality: Chelsea, Mich., Lewis Publications, Inc.,
be the result of septic-tank effluent.                          336 p.
                                                        Geldreich, E.E, and Kenner, H.L., 1969, Concepts of fecal
                                                                streptococci in stream pollution: Journal of the Water
    Organic substanceswere not detected, but                    Pollution Control Federation 41; part 2, A336-352.
the absence of such substances in ground                Hollyday, E.F., and Goddard, P.L., 1980, Ground-water availability in
water does not demonstrate nor eliminate a                      carbonate rocks of the Dandridge area, Jefferson County,
possible direct hydraulic connection between                    Tennessee: U.S. Geological Sutvey Water Resources
the field lines and ground water. Results                       Investigations Report 79-1263, 50 p.
                                                        Madison, R.J., and Burnett, J.O., 1985, Overview of the occurrence
from these analyses are inconclusive as to                      of nitrate in ground water of the Unites States, jt~ National
whether or not septic-tank effluent is affecting                Water Summaty: U.S. Geological Survey Water-Supply Paper
ground-water quality.                                           2275,467 p,
                                                        Miller, D.W., 1980, Waste-disposal effects on ground water: BerkIey,
                                                                Calif., Premier Press, 512 p.
    Bacteria were not detected in any of the            Mull, D.S., Lieberman, T.D., Smoot, J.L., and Woosley, L.H., 1988,
three domestic wells sampled for this study.                    Application of dye-tracing techniques for determining
The highest concentrations of fecal coliform                    solute-transport characteristics of ground water in karst
colonies were in water from springs Wm:O-9                      terranes: U.S. Environmental Protection Agency, Region 4,
and Wm:O-11.                                                    Manual EPA 904/6-88-001, 103 p.
                                                        Pitt, W.A.J., Jr., Mattraw, H.C., Jr., and Klein, H., 1975, Ground-
                                                               water quality in selected areas serviced by septic tanks, Dade
     Only the results of sampling for optical                   County, Florida: U.S. Geological Survey Open-File Report
brighteners gave conclusive evidence that                      75-607, 82 p.
septic-tank effluent is affecting ground-water          Wailer, B.G., Howie, Barbara, and Causaras, C.R., 1987, Effluent
                                                               migration from septic tank systemsin two different lithologies,
quality. One of the four springs tested in the                 Broward County, Florida: U.S. Geological Survey Water-
study areas contained optical brighteners.                     Resources Investigations Report 87-4075, 22 p.
This indicated that this spring (Wm:O-9) is             Wilson, T.M., Reinhard, J.D., Gordon, J.A., and Ogden, AE., 1988,
hydraulically connected to the septic-tank field               A study of septic tank systems in Sullivan County, Tennessee:
lines.                                                         TennesseeValley Authority Report TV 65598a, 89 p.


To top